Ambient laminar gas flow distribution in laser processing systems

ABSTRACT

A method and apparatus for annealing semiconductor substrates is disclosed. The apparatus has an annealing energy source and a substrate support, with a shield member disposed between the annealing energy source and the substrate support. The shield member is a substantially flat member having a dimension larger than a substrate processed on the substrate support, with a window covering a central opening in the substantially flat member. The central opening has a gas inlet portal and a gas outlet portal, each in fluid communication with a gas inlet plenum and gas outlet plenum, respectively. A connection member is disposed around the central opening and holds the window over the central opening. Connection openings in the connection member are in fluid communication with the gas inlet plenum and gas outlet plenum, respectively, through a gas inlet conduit and a gas outlet conduit formed through the connection member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Non Provisional patentapplication Ser. No. 13/204,068, which claims the benefit of U.S.Provisional Patent Application Ser. No. 61/444,973 filed Feb. 21, 2011,both of which are herein incorporated by reference.

FIELD

Embodiments disclosed herein relate to methods and apparatus formanufacturing semiconductor devices. More specifically, apparatus andmethods of annealing semiconductor substrates are disclosed.

BACKGROUND

Thermal annealing is a commonly used technique in semiconductormanufacturing. A material process is generally performed on a substrate,introducing a material desirous of including in the substrate, and thesubstrate is subsequently annealed to improve the properties of thematerially changed substrate. A typical thermal anneal process includesheating a portion of the substrate, or the entire substrate, to ananneal temperature for a period of time.

During the thermal anneal, the material introduced to the substratetypically migrates through the substrate, but some of the material mayvolatilize into the vapor space above the substrate. These materials mayhave elements such as phosphorus, arsenic, and other potentially toxicelements that must be removed from the vapor space before it can bevented into the environment. In addition, atmospheric components, suchas oxygen, that react with substrate materials are typically excludedfrom the processing environment to avoid unwanted reactions with thesubstrate.

Typically, a chamber enclosure is used to regulate the processingenvironment and confine any potentially toxic gases from being released.The chamber vapor space is continuously purged with inert gas, which isevacuated into an abatement system, resulting in a large flow of gas tobe scrubbed. Additionally, the requirement of using a chamber imposesother restrictions, such as sealing and factory access to the chamberinterior, that add cost to the overall system.

Thus, there remains a need for efficient and cost-effective apparatusand methods for regulating the processing environment surroundingsubstrates undergoing thermal anneal processes.

SUMMARY

An apparatus is disclosed for annealing semiconductor substrates. Theapparatus has an annealing energy source and a substrate support, with ashield member disposed between the annealing energy source and thesubstrate support. The shield member is a substantially flat memberhaving a dimension larger than a substrate processed on the substratesupport, with a window covering a central opening in the substantiallyflat member. The central opening has a gas inlet portal and a gas outletportal, each in fluid communication with a gas inlet plenum and gasoutlet plenum, respectively. A connection member is disposed around thecentral opening and holds the window over the central opening.Connection openings in the connection member are in fluid communicationwith the gas inlet plenum and gas outlet plenum, respectively, through agas inlet conduit and a gas outlet conduit formed through the connectionmember.

The shield member has two plates fastened together so as to form the gasinlet plenum and gas outlet plenum within the shield member. More thanone gas inlet portal and gas outlet portal may be provided in thecentral opening by forming notches in one plate of the shield member.One set of notches abuts the window to form the gas inlet portals, andanother set of notches abuts the other plate to form the gas outletportals. A plurality of openings is provided through the shield memberfor flowing gas into the space between the shield member and thesubstrate or substrate support.

A method of thermally processing a substrate comprises defining aprocessing zone in a portion of the substrate surface, the processingzone having a dimension smaller than the substrate surface, enclosingthe processing zone with a shield member that defines a processingvolume proximate the processing zone, flowing a first purge gas throughthe processing volume, and directing annealing energy through theprocessing volume to the processing zone. A second purge gas may beprovided through openings in the shield member spaced apart from theprocessing volume, such that the first and second purge gases flowradially outward from the processing volume through the space betweenthe shield member and the substrate support.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is an isometric view of an annealing apparatus according to oneembodiment.

FIG. 2A is a perspective view of a shield member according to anotherembodiment.

FIG. 2B is a cross-sectional view of the shield member of FIG. 2A.

FIG. 2C is a cross-sectional view of the shield member of FIG. 2A alonga different section line.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation.

DETAILED DESCRIPTION

FIG. 1 is an isometric view of a novel apparatus 100 for thermallyannealing a semiconductor substrate. The anneal apparatus 100 has asource of annealing energy 108, a substrate support 110, and a shieldmember 112 disposed between the substrate support 110 and the source ofannealing energy 108. The substrate support 110 may be disposed on abase 102, and the source of annealing energy 108 may be mounted on asupport panel 106, which in turn may be mounted on a wall 104 risingfrom the base 102.

The source of annealing energy 108 may be a radiant source, such as alaser, and generally produces annealing energy 118 that is directedtoward the substrate support 110 through an opening 116 in the shieldmember 112. In one embodiment, the source of annealing energy 108 maycomprise two lasers adapted to provide a tailored annealing energy. Forexample, a first laser may provide a preheat energy while a second laserprovides an annealing energy.

The shield member 112 is fastened to the support panel 106 by one ormore brackets 114, which hold the shield member 112 in a fixed positionwith respect to the source of annealing energy 108, such that theannealing energy 118 passes through the opening 116 at all times. Thebrackets may be configured such that the shield member 112 may beremoved for cleaning, if desired, and the same shield member 112, oranother substantially identical shield member 112, installed. Asubstrate disposed on the substrate support 110 is generally larger thanthe opening 116, but smaller than the shield member 112. Successiveportions of the substrate are positioned to receive the annealing energy118 through the opening 116 by moving the substrate support 110. Thesubstrate support 110 may be a precision x-y stage operated by acontroller 120.

FIG. 2A is a perspective view of a shield member 200 according toanother embodiment. The shield member 200 may be used in the apparatus100 of FIG. 1. The shield member 200 has a substantially flat member202, formed from a first plate 204 and a second plate 206, which platesmay be fastened together by fasteners 208. In one embodiment, threadedholes may be bored to accept screws. Openings 220 in the substantiallyflat member 202 allow a purge gas to be provided through thesubstantially flat member 202 to the space between the shield member 200and a substrate disposed on a substrate support below the shield member,as in FIG. 1.

Although two openings 220 are shown in FIG. 2A, any number may beprovided. The openings 220 may be arranged in ranks according toconcentric circles, in some embodiments. A shield member 200 havingranks of concentric openings 220, with at least one rank disposed nearthe central region of the shield member 200 and one rank disposed nearthe periphery, may support differential pumping of gas from between theshield member 200 and a work surface such as the stage 110 of FIG. 1.Vacuum sources having different flow rates may be coupled to thedifferent ranks to accomplish differential pumping. A vacuum sourcehaving a low flow rate may be coupled to a peripheral rank while avacuum source having a high flow rate may be coupled to a central rank.

The substantially flat member 202 has a central opening 116, as in FIG.1, that allows annealing energy to pass through the shield member 200and irradiate a substrate. A window 214 covers the central opening 116of the substantially flat member 202.

A connection member 210 is disposed around the central opening 116 ofthe substantially flat member 202, and may attach the window 214 to thefirst plate 204. The connection member 210 has a central opening 212that registers with the central opening 116 of the substantially flatmember 202. In some embodiments, the central opening 212 of theconnection member 210 is coaxial with the central opening 116 of thesubstantially flat member 202. Additionally, the central opening 212 mayhave a radius that is substantially the same as a radius of the centralopening 116 of the substantially flat member 202. The radius of thecentral opening 212 may also be larger or smaller than that of thecentral opening 116 of the substantially flat member 202.

A gas inlet 218 and gas outlet 216 are provided in a surface of theconnection member 210 to allow a purge gas to be provided to the spacebetween the window and a substrate disposed on the substrate support, asin FIG. 1 and as described further below. The connection member 210 maybe fastened to the substantially flat member 202 using fasteners 222,which may be screws.

FIG. 2B is a cross-sectional view of a portion of the shield member 200of FIG. 2A. The annealing energy 118 from FIG. 1 is shown passingthrough the window 214 and irradiating a substrate 240. The gas inlet218 in the surface of the connection member 210 fluidly communicateswith a gas inlet conduit 236 and a gas inlet plenum 228, which surroundsthe central opening 116. Openings 230 formed in an inner wall 242 of thefirst plate 204 fluidly communicate with the gas inlet plenum 228 toflow a gas into the central opening 116 proximate the window 214.Dividers 232 are disposed between the openings 230 to provideback-pressure to fill the gas inlet plenum 228, making the openings 230discrete one from the other. Any number of dividers 232 may be used,depending on the size of the openings 230 desired. The dividers 232 alsosupport the window 214 above the openings 230, bounding the inlet gasflow toward the substrate 240.

The gas outlet 216 in the surface of the connection member 210, whichmay be an annular member, fluidly communicates with a gas outlet conduit244 and a gas outlet plenum 224, which also surrounds the centralopening 116. In the embodiment of FIG. 2B, the gas outlet plenum has aradius and/or circumference larger than that of the gas inlet plenum228, but it is not required. The gas outlet plenum 224 is formed as achannel between the first plate 204 and the second plate 206. Openings226 between the first and second plates 204 and 206 allow gas to flowfrom the central opening 116 into the gas outlet plenum 224, and thenout through the gas outlet conduit 244 and the gas outlet 216.

The central opening 116 has a first end 256 proximate the window 214,and a second end 258 between the first end 256 and the substrate 240.The first and second ends 256 and 258 together define an axissubstantially perpendicular to a plane formed by the substantially flatmember 202. The openings 230 may be disposed around a circumference ofthe central opening 116. In the embodiment of FIG. 2A, the openings 230,which may be gas inlet portals, are positioned proximate the first end256 of the central opening 116, while the openings 226, which may be gasoutlet portals, are proximate the second end 258 of the central opening116. The openings 230 may be coplanar or substantially coplanar, and theopenings 226 may also be coplanar or substantially coplanar. Dependingon the thickness of the second plate 206 and the size of the openings226, the openings 226 may be spaced apart from both the first end 256and the second end 258 of the central opening 116.

The connection member 210 is a substantially continuous member, whichmay be fastened to the substantially flat member 202 by fasteners 222,which may be screws. In the embodiment of FIG. 2B, the screws are shownextending into the first plate 204, but they may be extended into thesecond plate 206 as well, thereby further enhancing fastening of thefirst plate 204 and the second plate 206, if desired. The connectionmember 210 may have a notch 246 formed in an inner wall 262 thereof tofit the outer edge of the window 214. When fastened down, the connectionmember 210 holds the window 214 in place over the central opening 116 byoperation of the notch 246.

FIG. 2C is a different cross-sectional view of a portion of the shieldmember 200 of FIG. 2A along a different section line. In this sectionview, the gas inlet 218, gas outlet 216, gas inlet conduit 236, the gasoutlet conduit 244, the openings 226, and the dividers 232 are notvisible. The openings 230 form a continuous gas path with the gas inletplenum 228 in this view. The gas outlet plenum 224 is visible, butseparated from the central opening 116 at the location of this section.No openings in the connection member 210 are visible in this section,indicating the continuity of the connection member 210.

The openings 220 formed through the substantially flat member 202 arevisible in this view. Each opening 220 communicates with an opening 234on an opposite face of the substantially flat member 202, providing aconduit through the substantially flat member 202 for gas to flow fromone face to the other. Thus, in addition to the gas provided to thecentral opening 116 of the substantially flat member 202, as shown inFIG. 2B, a gas may be provided to the openings 220 to enhance the gasflow between the shield member 200 and the substrate 240.

In operation, a substrate is positioned on the substrate support facingthe shield member 200. A purge gas source is connected to the gas inlet218 of the connection member 210, and to each of the openings 220 in thesubstantially flat member 202. The purge gases connected to eachlocation may be the same or different. In one embodiment, a source ofnitrogen gas is connected to each location. A vacuum source may beconnected to the gas outlet 216.

Purge gas flows through the gas inlet conduit 236 into the gas inletplenum 228, distributing the purge gas around the central opening 116.The purge gas flows uniformly through the openings 230, radially inwardalong the substrate-facing surface 264 of the window 214. The purge gasflow curves under pressure to flow toward the substrate 240 near thecenter of the central opening 116. As the purge gas approaches thesubstrate 240, the flow curves into a radial outward flow along theexposed surface 248 of the substrate. The radial outward gas flowcontinues to an outer edge of the shield member 200, which is beyond anouter edge of the substrate 240, maintaining a purge gas flow from theprocessing zone 254 of the substrate 240 to its perimeter, thusminimizing any intrusion of unwanted gases from the environment into theprocessing area. Purge gas provided to the openings 220, and flowingthrough the substantially flat member 202 to the openings 234, enhancesthe radial outward flow of purge gas, further limiting intrusion ofundesired species.

The substrate-facing surface 264 of the window 214, along with the innerwall 242 of the first plate, an inner wall 250 of the second plate, andthe exposed surface 248 of the substrate 240 cooperatively define aprocessing volume 252 above a processing zone 254 of the substratesurface 248. As the annealing energy 118 anneals the substrate surface248, gases may be released from the substrate surface that are desirousof collection and abatement. A vacuum source may be connected to the gasoutlet 216 to establish an outlet flow of purge gas laden with substrategases emitted into the processing volume 252. Typically, flow of gas tothe gas inlet 218 is set to a value larger than the gas flow to the gasoutlet 216, under influence of the vacuum source, to maintain the radialoutward flow of purge gas from the processing zone 254 to the peripheryof the shield member 200, beyond the periphery of the substrate 240. Itmay be desired, in some embodiments, for a large majority of the purgegas provided to the central opening 116 to be exhausted through the gasoutlet 216. In such embodiments, a small flow of purge gas from theprocessing zone 254 to the periphery of the shield member 200 remains,which is further diluted by purge gas provided through the openings 220.If desired the purge gas flowing to the periphery of the shield member200 may be collected and subjected to further abatement.

Flow of the purge gas toward the substrate is established by therelative positions of the gas inlet openings 230 and the gas outletopenings 226. It should be noted that reversing the positions of the gasinlet and outlet openings 230 and 226 (or simply reversing connectionsof gas source and vacuum source) may provide an upward flow in thecentral opening 116. In some embodiments, a downward flow of purge gasmay be preferred to prevent deposition of substrate exudates on thewindow and resultant clouding of the window. In other embodiments,complete abatement may be desired and achieved by upward flow of purgegas in the central opening. In such embodiments, purge gas providedthrough the openings 220 of the substantially flat member 202 may flowradially outward and radially inward to accomplish both objectives ofpreventing intrusion of gases from the environment at the periphery ofthe shield member 200 and collecting off-gas from the substrate.

It should be noted that providing a gas outlet within the centralopening 116 is optional. In some embodiments, the gas inlet openings 230may provide purge gas to the processing volume 252, and the purge gasmay all flow out of the processing volume 252 between the substantiallyflat member 202 and the substrate.

In other embodiments, a purge gas may be configured to flow across theprocessing zone 254 of the substrate surface 248 by providing a gasinlet opening on one side of the central opening 116 and a gas outlet onan opposite side of the central opening 116, such that a purge gasprovided to the gas inlet will flow linearly across the substrate to thegas outlet, removing any off-gas.

In the embodiments described above in connection with FIGS. 2B and 2C,the openings 230 are formed in alignment with a radius of the centralopening 116, such that gas flowing through the openings 230 flowsinitially inward along the radius toward the center of the centralopening 116. If desired, a circular flow or vortex flow may be providedby forming the openings 230 along an axis angled with respect to aradius drawn through a center of each opening 230 in the plane of thesubstantially flat member 202, such that gas flowing through eachopening 230 has an angular flow component as well as a radial flowcomponent. If desired, the openings 230 may be formed with an axialangle, as well, to provide an axial flow component, either toward thewindow 214 or toward the substrate 240. Such flow patterns may be usefulin avoiding local concentrations of off-gas that may be harmful tocomponents of the shield member 200.

The substantially flat member 202 may be aluminum, or any structuralmaterial unlikely to affect substrates adversely. The connection member210 may be a polymer, such as plastic or ceramic, such as alumina, andmay be a refractory material, if desired.

The shield member 200 is typically larger than the substrate 240, insome cases much larger. A ratio of the areal extent of the shield member200 to the areal extent of the substrate 240 is between about 2 andabout 10, for example about 5. The shield member 200 thus functions likea “semi-infinite” plate, relative to the substrate 240, for establishingan outward gas flow field. This provides a relatively large managedatmosphere between the shield member 200 and the substrate support 110(FIG. 1) within which the substrate 240 moves as the anneal proceeds. Inan embodiment for processing 300 mm wafers, the shield member 200 mayhave a diameter between about 500 mm and about 1,000 mm, for exampleabout 700 mm.

A distance “d” between the substrate surface 248 and a lower surface 260of the shield member 200 is typically much smaller than a dimension(e.g. diameter, radius, diagonal length) of the substrate 240. A ratioof the dimension of the substrate to the distance “d” is typicallybetween about 50:1 and about 200:1, for example about 100:1. For anexemplary 300 mm circular substrate, the distance “d” may be about 3 mm.For most embodiments, the distance “d” is between about 1 mm and about20 mm, such as between about 2 mm and about 10 mm. A small distance “d”,relative to the substrate 240 dimension, affords a uniformly brisk flowof purge gas from the processing zone 254 of the substrate 240 to theperiphery thereof, maximizing exclusion of environmental gases from theprocessing volume 252.

The central opening 116 is generally sized to accommodate the type anddimension of the annealing energy 118 admitted therethrough. In anembodiment using a shaped annealing energy, such as a laser annealembodiment having an anneal beam with an optically defined shape, thecentral opening may be sized and shaped with minimal edge clearancerelative to the anneal beam. For example, if the anneal beam hasdimension of 10 mm×30 mm, the central opening 116 may have dimension of11 mm×31 mm. Such sizing may minimize substrate off-gas contacting thewindow 214. In other embodiments, the central opening 116 may be shapedas a cylindrical hole, as shown in FIGS. 1-2C, and may have a radiusbetween about 10 mm and about 100 mm, for example about 25 mm. Asmentioned above, the central opening 212 of the connection member 210may be the same size and shape as the central opening 116 of thesubstantially flat member 202, or a different size and shape. It ispreferred that the central opening 212 of the connection member 210 belarger than the annealing energy 118 passing through the window 214 toavoid thermal degradation of the connection member 210.

In one embodiment, the substantially flat member has a thickness betweenabout 50 mm and about 250 mm, such as between about 100 mm and about 200mm, for example about 125 mm. Each of the first plate 204 and the secondplate 206 has a thickness approximately half the thickness of thesubstantially flat member 202, such that the thicknesses of the firstand second plates 204 and 206 are approximately equal, except near thecentral opening 116.

The openings 230 may be formed as rectangular openings oriented alongradii of the central opening 116, and may have dimension in the angulardirection between about 0.1 mm and about 5 mm, such as between about 0.5mm and about 2.0 mm, for example about 1.0 mm. The dimension of theopenings 230 in the axial direction (along the axis of the centralopening 116) may be between about 0.1 mm and about 5 mm, such as betweenabout 0.5 mm and about 2.0 mm, for example about 1.0 mm. As such, theopenings 230 may be substantially square in shape. It should be notedthat the openings 230 may have any convenient shape in cross-section,such as rectangular, circular, oval, or any polygonal or irregular shapethat may be desired. The openings 226 may be sized and shaped the sameas the openings 230, or according to any size and shape to achieve adesired fluid flow.

The inlet and outlet gas plenums 228 and 224, respectively, havedimensions in general flow agreement with dimensions of the openings 230and 226, respectively. In one embodiment, the inlet and outlet gasplenums 228 and 224 are channels having a generally rectangularcross-section and surrounding the central opening in an annular fashion.The channels have a width between about 0.1 mm and about 5 mm, such asbetween about 0.5 mm and about 4 mm, for example about 2.0 mm. A centralaxis of the gas inlet plenum 228 may be spaced apart from the wall 242of the central opening 116 between about 1.0 mm and about 10 mm, forexample about 5 mm, while the central axis of the gas outlet plenum 224may be spaced apart from the wall 242 of the central opening 116 betweenabout 1.0 mm and about 10 mm, for example about 6 mm. It should be notedthat the two plenums 228 and 224 may be spaced the same distance fromthe wall 242 if one of the gas conduits 236 and 244 is angled to avoidconflict with a plenum.

Axial distance between the openings 230 and the openings 226 is relatedto thickness of the substantially flat member 202, in the embodiments ofFIG. 1-2C, because the openings 226 are formed by space between the twoplates 204 and 206. In one embodiment, the openings 230 and 226 arespaced apart between about 50 mm and about 250 mm, such as between about80 mm and about 120 mm, for example about 100 mm.

The connection member 210 may have thickness between about 50 mm andabout 500 mm, such as between about 100 mm and about 200 mm, for exampleabout 125 mm. The connection member 210 may have a thickness selected todefine a distance between the window 214 and the substrate 240. Thedistance between the window 214 and the substrate 240 may be increased,if desire, to reduce deposition of substrate exudates on the window 214in some embodiments. The gas inlet and outlet conduits 236 and 244,respectively, and the respective gas inlet and outlet 218 and 216, arealso sized in flow agreement with the other components of the purge gascircuit, with diameter of each typically between about 1.0 mm and about10 mm, such as between about 3 mm and about 7 mm, for example about 5mm. The outer radius of the connection member 210 is selected providespace for the gas inlet and outlet 218 and 216, respectively, and forthe fasteners 222. In one embodiment, the outer radius of the connectionmember 210 is between about 50 mm and about 150 mm, such as betweenabout 75 mm and about 125 mm, for example about 100 mm.

The purge gas openings 220 formed in the substantially flat member 202are generally spaced between the central opening 116 and the peripheryof the shield member 200. In one embodiment, the purge gas openings 220are spaced from the center of the shield member 200 a distance betweenabout 50 mm and about 400 mm, such as between about 100 mm and about 200mm, for example about 150 mm.

The window 214 is typically positioned further from the substratesurface 248 than the lower surface 260 of the substantially flat member202 to avoid unwanted deposition on, and clouding of, the window 214.For this reason, the thickness of the connection member 210 may beadjusted to provide the desired elevation. In one embodiment, a ratio ofthe distance between the window 214 and the substrate surface 248 to thedistance between the lower surface 260 and the substrate surface 248 isbetween about 10:1 and about 100:1, such as between about 15:1 and about50:1, for example about 16:1. In an embodiment wherein the distance “d”is about 3 mm, the window 214 may be spaced apart from the substratesurface 248 at least about 50 mm.

In one embodiment, the shield member 200 may provide a heat shield forcomponents that may be sensitive to radiation. In some embodiments, asubstrate disposed on the substrate support facing the shield member 200may be heated. Radiation emitted by the heated substrate may damageoptical instruments arranged to tune the energy 118 directed toward thesubstrate or arranged to monitor the condition of the substrate. If theshield member 200 is located between the substrate and the optics, theshield member 200 may be cooled, for example by flowing a cooling mediumthrough channels formed between the two plates 204 and 206, to reduceradiation absorbed by the optics.

As described above, the substrate may emit byproducts during thermalprocessing. If such byproducts are deposited on the shield member 200,as may happen particularly if the shield member 200 is cooled, theshield member 200 may be removably attached to a support member such asthe support 106 of FIG. 1. The shield member 200 may then be quicklyremoved or swapped for cleaning.

A method of annealing a semiconductor substrate includes positioning thesubstrate on a substrate support facing a source of annealing energy anddisposing a shield member between the substrate and the energy source. Acentral opening is provided in the shield member to admit the annealingenergy through to the substrate. A projection of the central openingonto the substrate surface defines a processing zone on the substratesurface. A window is provided covering the opening and the processingzone, and together with an inner wall of the central opening and thesubstrate surface opposite the window, defines a processing volumearound the processing zone. The shield member described above inconnection with FIGS. 1-2C may be used to perform this method.

A purge gas is flowed through the processing volume, and may bepartially or completely evacuated from the processing volume by applyinga vacuum source. Purge gas not evacuated from the processing volume maybe allowed to flow out of the processing volume through a space betweenthe substrate and the shield member. A second purge gas may be providedto the space between the substrate and the shield member, at a locationbetween the center and the periphery of the shield member, to enhancethe radial flow of purge gas. Radial flow of purge gas outward from thecenter to the periphery prevents intrusion of unwanted gases from theenvironment into the processing volume.

In a typical anneal process for a 300 mm wafer, a purge gas may beprovided through the connection member at a purge gas feed flow ratebetween about 10 sLm and about 50 sLm, such as between about 20 sLm andabout 40 sLm, for example about 30 sLm. A vacuum source may beconfigured to draw a flow rate of purge gas between about 10% and about110% of the purge gas feed flow rate, such as between about 40% andabout 99% of the purge gas feed flow rate, for example about 90% of thepurge gas feed flow rate. The second purge gas provided to theperipheral openings 220 may be provided at a flow rate between about 5sLm and about 50 sLm for each opening 220, such as between about 10 sLmand about 30 sLm per opening, for example about 15 sLm per opening.Purge gases suitable for most embodiments include nitrogen gas, argon,helium, hydrogen, other inert or noble gases, and mixtures thereof. Thefirst purge gas provided to the connection member may be the same as, ordifferent from, the second purge gas provided to the peripheral openingsof the substantially flat member.

Annealing energy is directed through the window to the substrate surfaceto anneal a portion of the substrate surface in the processing zone. Thesubstrate may be moved according to any desired pattern to successivelyanneal portions of the substrate surface. The entire substrate surfacemay be annealed in this sequential fashion, if desired.

The shield member described herein in various embodiments is useful forcontrolling the atmosphere of the processing volume proximate theprocessing zone of the substrate by excluding environmental gases fromthe processing volume. It should be noted that some embodiments in whichsuch a shield member is used may utilize a reactive atmosphere, ratherthan an inert atmosphere. In such embodiments, a reactive gas mixture,for example a gas mixture including oxygen gas, ammonia, or anotherreactive gas, may be provided through the gas inlet openings 230.

A shield member, as described herein in connection with FIGS. 1-2C, maybe made by machining two plates of desired thickness. Two aluminumplates having a desired diameter may be bored through the center to forma central opening such as the central opening 116 of FIG. 1. The secondplate 206 may be fashioned by machining a circular or annular groove adesired distance from the central opening, and then machining theopenings 226 from the wall of the central opening along a radius to theannular groove. The first plate 204 may be fashioned by machining away aportion of the thickness of the plate outside a selected radius from thecenter, the selected radius being smaller than the radius of the annulargroove formed in the second plate 206. The first plate 204 may then beinverted, and the openings 230 formed in the upper surface thereofaccording to a process similar to that used for the openings 226. Thegas inlet and outlet conduits 236 and 244 are bored into the two platesat selected locations, according to the depths of the annular spacesformed by the two plates. The two plates 204 and 206, thus formed, maybe bored for fasteners, and the openings 220 bored through the plates.The connection member 210 may be formed by molding plastic or ceramic,or a disk shaped plastic or ceramic member may be worked with anabrasion tool to form the central opening, notch, gas conduits, andfastener bores.

Other channels and bores may be provided in the first and second plates204 and 206, if desired, to accommodate thermal control fluids, such ascooling fluids, cooperatively defining thermal control fluid conduits.Any channel configuration may be machined into the plates to form acooling channel, if desired, to give the shield member heat shieldproperties. Such capabilities may be useful for embodiments in which asubstrate is subjected to background heating.

Embodiments described herein provide a shield for a thermal annealingapparatus, the shield having a substantially flat member, which may beconstructed from a material having metal, such as aluminum, with acentral opening defined by a wall, the wall having a gas inlet portaland a gas outlet portal, the gas inlet portal in fluid communicationwith a gas inlet conduit formed in the member, and the gas outlet portalin fluid communication with a gas outlet conduit formed in the member.

The substantially flat member may have a first plate, a second plate,and a window covering the central opening. The window may cover thecentral opening at the first plate, and the gas inlet and outletconduits may extend to openings in the first plate. The central openingmay have a first end and a second end that together define an axissubstantially perpendicular to a plane defined by the substantially flatmember, with plurality of gas inlet portals, which may be substantiallycoplanar, connected by a first channel formed between the first plateand an annular member that attaches the window to the first plate and aplurality of gas outlet portals, which may also be substantiallycoplanar, connected by a second channel formed between the first plateand the second plate, wherein the first channel is in fluidcommunication with the gas inlet portals and the second channel is influid communication with the gas outlet portals.

The gas inlet portals may be disposed around a circumference of thecentral opening, and may be in fluid communication with a gas inletplenum. The gas outlet portals may be disposed around a circumference ofthe central opening, and may be in fluid communication with a gas outletplenum, which may have a circumference larger than a circumference ofthe gas inlet plenum.

A connection member, for example a fastener, which may be a polymer, maybe fastened to the substantially flat member. The connection member maybe annular and coaxial with the central opening, and the window may bedisposed between the connection member and the substantially flatmember. The connection member may have a central opening ofsubstantially the same dimension as the central opening of thesubstantially flat member.

While the foregoing is directed to embodiments of the invention, otherand further embodiments of the invention may be devised withoutdeparting from the basic scope thereof.

What is claimed is:
 1. An apparatus for annealing a semiconductorsubstrate, comprising: a shield member comprising: a substantially flatmember having an upper surface and a lower surface and a central openingdefined by a wall having: a first end at the upper surface; a second endat the lower surface, wherein the first end and the second end define anaxis substantially perpendicular to the substantially flat member; a gasinlet portal between the first end and the second end; and a gas outletportal between the first end and the second end, wherein the gas inletportal and the gas outlet portal are spaced apart along the axis; and awindow covering the central opening and coupled to the first end of thewall.
 2. The apparatus of claim 1, wherein the gas inlet portal is influid communication with a gas inlet conduit formed in the substantiallyflat member, and the gas outlet portal is in fluid communication with agas outlet conduit formed in the substantially flat member.
 3. Theapparatus of claim 1, wherein the apparatus further comprises asubstrate support and a ratio of a distance between the window and thesubstrate support to a distance between the lower surface and thesubstrate support is between 10:1 and 100:1.
 4. The apparatus of claim3, wherein the ratio is between 15:1 and 50:1.
 5. The apparatus of claim1, wherein the apparatus further comprises a substrate support and adistance between the lower surface and the substrate support is 3 mm. 6.The apparatus of claim 1, wherein the central opening has a dimension of11 mm by 31 mm.
 7. The apparatus of claim 1, wherein the central openingis shaped as a cylindrical hole.
 8. The apparatus of claim 7, whereinthe central opening has a radius between 10 mm and 100 mm.
 9. Theapparatus of claim 8, wherein the central opening has a radius of 25 mm.10. The apparatus of claim 1, wherein the gas inlet portal or the gasoutlet portal has a shape selected from the group consisting ofrectangular, circular, oval, and polygonal.
 11. The apparatus of claim10, wherein the gas inlet portal or the gas outlet portal isrectangular.
 12. The apparatus of claim 11, wherein the gas inlet portalor the gas outlet portal has a dimension in a direction circumferentialwith respect to the axis between 0.1 mm and 5 mm.
 13. The apparatus ofclaim 11, wherein the gas inlet portal or the gas outlet portal has adimension in a direction parallel to the axis between 0.5 mm and 2 mm.14. The apparatus of claim 1, wherein the gas inlet portal is in fluidcommunication with a gas inlet plenum disposed around the centralopening, and the gas outlet portal is in fluid communication with a gasoutlet plenum disposed around the central opening.
 15. The apparatus ofclaim 14, wherein the gas inlet plenum or the gas outlet plenum is achannel having a rectangular cross-section.
 16. The apparatus of claim15, wherein the channel has a width between 0.1 mm and 5 mm.
 17. Theapparatus of claim 14, wherein a central axis of the gas inlet plenum orgas outlet plenum is spaced apart from the wall of the central openingbetween 1 mm and 10 mm.
 18. A shield for a thermal annealing apparatus,comprising: a substantially flat member having an upper surface and alower surface and a central opening defined by a wall having: a firstend at the upper surface; a second end at the lower surface, wherein thefirst end and the second end define an axis substantially perpendicularto the substantially flat member; a gas inlet portal between the firstend and the second end; and a gas outlet portal between the first endand the second end, wherein the gas inlet portal and the gas outletportal are spaced apart along the axis; a window covering the centralopening and coupled to the first end; and an annular connection memberattached to the substantially flat member in a coaxial relationship,wherein the window is disposed between the substantially flat member andthe annular connection member.
 19. The shield of claim 18, wherein theconnection member has a thickness between 50 mm and 500 mm.
 20. Theshield of claim 19, wherein the connection member has an outer radius ofbetween 50 mm and 150 mm.